Printers include an inkjet printer having a printhead with print nozzles used to print ink on print media. Typically, print data is generated by a computer and is sent to a printer memory where it is used by the printer to generate a bitmap of how the print nozzles will be fired to deposit ink drops as the printhead moves across the print media. The print media is advanced for the next print swath when the printer is through printing the present print swath. A multi-pass print swath is a print swath printed by two or more print passes (or print scans) of the printhead either before the print media is advanced or with the media being advanced less than the height of a print swath between print passes.
Shingling is an example of multi-pass printing known to those skilled in the art and is used for certain print modes to improve print quality. Shingling is an overlay print process whereby ink droplets are applied to a print medium in a distributed fashion. Print overlay techniques vary with typical shingling print algorithms using two, three, four or six or more print passes (print scans) per print swath to achieve full print coverage. In one known shingling application, the print media is advanced between print passes a distance equal to the print swath height divided by the number of print passes.
One example of two-shingling-pass printing uses a “checkerboard” shingling print algorithm, wherein the first printing pass prints only on the pixel locations of the print media corresponding to the black squares of a checkerboard, and wherein the second printing pass prints only on the pixel locations of the print media corresponding to the red squares of the checkerboard. To do this, the computer sends print data corresponding to the black squares or the red squares of the entire checkerboard to the printer memory for the corresponding print pass, wherein the print data corresponding to the red squares are made to be “don't print” print data for the first print pass and define the deterministic voids in the first print pass, and wherein the print data corresponding to the black squares are made to be “don't print” print data for the second print pass and define the deterministic voids in the second print pass.
What is needed is an improved method for printing shingling print data in a shingling print pass of a multi-shingling-pass print swath.